Which Australian external territory's flag was designed by Tony Couch?

Christmas Island’s flag was designed by Tony Couch.

Couch, a Sydney resident who had previously worked on Christmas Island, submitted the winning design in a 1986 territory-wide competition. The design combines a blue-and-green diagonal field, a golden bosun bird, the Southern Cross and a gold disc containing a green outline of the island.

The colors represent the surrounding sea and the island’s land. The bosun bird is a local form of white-tailed tropicbird and became one of the territory’s most recognizable symbols. The Southern Cross also reflects Christmas Island’s connection with Australia and the southern Pacific region.

The flag was announced as the competition winner on April 14, 1986, and became widely used in the community. It is often described as adopted in 2002, but Australian Government material has also noted that it was not formally adopted under Australian law. That status does not change the designer’s identity.